基于WRF模式对贵州一次山地暴雨数值模拟研究

Research on the numerical simulation of heavy rain in Guizhou mountains based on WRF model

采用中尺度天气模式WRFV3.6.1模拟发生在贵州西南部山区大暴雨天气,由于复杂的地形条件,数值模拟难度大。通过对降雨实况、高空对比分析,WRF模式能够很好模拟此次大暴雨天气过程。在此基础上,结合贵州地形下利用高分辨率的数值结果进行天气学诊断分析,得出:(1)WRF能够较好地模拟贵州一次山地暴雨天气过程的大尺度环境、降水分布,只是在贵州中北部的累计降水略偏大。(2)此次降雨过程存在着明显的低层辐合、高层辐散的形势配置,这有利于垂直运动的发展,进而产生剧烈的强对流天气。在垂直速度上也体现着在降雨中心存在着强对流发展,伸展高度高,垂直区域广。(3)低层深厚的湿层为暴雨发生提供了充足的水汽条件、充足的对流有效位能和比湿提供了能量条件、不稳定层结和强烈的上升运动也给此次大暴雨提供了有利配置,使得中尺度对流系统得到很好地发展,进而引发强降水。(4)700 h Pa上的垂直螺旋度与降水落区有着较好的对应关系,在实际业务中可以用来确定降雨落区,为确定落区提供科学依据。

Numerical simulation of a storm in southwestern Coteau area in Guizhou with a mesoseale model WRFV3.6.1 reveals the process of the storm, although the intricate topographic condition increases the difficulties. Combining it with high - resolution data and the topography of Guizhou to analyze the data and the result shows ： ① the WRF model can decently simulate large - scale environment and rainfall distribution of a heavy rain in Guizhou moumains, except that the accumulative precipitation of north - central Guizhou is slightly larger. ② low - level con- vergence and upper - level divergence clearly exist in this precipitation process,which are in favor of the progress of vertical movement, and cause severe convection weather. Also in the vertical direction, it shows the severe convec- tion progress, high extended height and wide vertical zone. ③The wet layer in lower air provides enough water vapour condition, enough convection and specific humidity, so does the unstable stratification and the strong ascending motion,the intermediate convective system, as a result,is well developed to cause a heavy rain. ④The vertical helieity of 700 hPa is well corresponding to rainfall area,which can provide scientific basis to confirm rainfall area in practical operation.